The use of laser devices in information-processing, display, or optical radar applications, requires the development of economical means for rapidly scanning and/or deflecting a high-resolution spot of coherent light.
A number of means of deflection have been suggested and reduced to practice. These have ranged from rotating mirrors to electro-optical systems. All of these systems require at least one "moving" element, e.g. a piezo-electric element caused to vibrate, a magnetorestrictive device controlled electrically, or mirrors revolving on a drum or oscillated by a galvanometer.
In order to obtain highly accurate movements, the known devices must resort to sophisticated electrical and/or mechanical means which increases the cost of these systems, thus making them unsuitable for many commercial applications. Furthermore, even with these expensive and sophisticated means, errors inherent in any moving system make them impractical, in principle, for many applications.
All deflection/scanning devices must address themselves to the following points with respect to function and usefulness: (1) What are the losses in the system due to the diminishing of the light intensity, (2) What are the aperture limitations, or what is the largest number of high-resolution spots obtainable in a given system with a given aperture, (3) What are the limitations imposed by diffraction losses, or in practical terms, how does the device cope with the continuous spreading of the laser beam, (4) Will the deflection system result in a linear scan pattern, i.e. will the distances between each of the resolvable spots be uniform, and finally (5) What is the largest number of high-resolution spots obtainable with the system for practical applications
Without a demonstrable solution to these questions, no scanning/deflection system can hope to be useful; it would remain merely an anomaly.